Serendipitous and Targeted Synthesis of High Nuclearity Clusters—Carbonate and Oxalate Encapsulating Silver Alkynides

Abstract

Silver coordination compounds of the [Ag 3 L 2 ] (where L = t Bu-CC) family having perchlorate counterions exhibit template-driven self-assembly of the common square pyramidal building block. This behavior is similar to previously described observations; however, important differences arise from counterion−silver interactions. Penta-and hexameric clusters encapsulating chloride and oxalate, respectively, were crystallographically characterized. A high nuclearity cluster [(CO 3 ) 3 (H 2 O)⊂Ag 38 L 20 ] 12+ was formed upon extended exposure to an ambient atmosphere by trapping three carbonates and one water molecule.

Oxocarbon Anions Templated in Silver Clusters

“…The bond lengths of C49-O28 (1.253(13) Å) and C50-O26 (1.175(14) Å) are shorter than C49-O27 (1.321(14) Å) and C50-O25 (1.420(17) Å), which confirms the trans -configured CO double bonds in the oxalate anion. In the case of [Ag 18 (C 2 O 4 )­(CC t Bu) 12 ]­(ClO 4 ) 4 , dihedral angles of oxalate lie between 61 and 67°, showing a larger torsion angle between two carboxylate groups with C–O bond lengths in a range of 1.25(1)–1.29(1) Å. Two [Ag 16 (C 2 O 4 )­{S 2 P­(OEt) 2 } 12 ] 2+ motifs are enantiomers and dimerize to become [Ag 16 (C 2 O 4 )­{S 2 P­(OEt) 2 } 12 ] 2 4+ (Figure c).…”

“…One of the well-known strategies is to use macrocyclic ligands that form porous organic cages, which show a good perspective in adjusting the inner pore size and encapsulating well-dispersed metal aggregates. , In this context, the macrocycle with donor atoms such as O, N, or S atoms reveals great affinity to the attached guest cluster and great stability due to the high steric hindrance of the aromatic rings. , However, the size and the geometry of the encapsulated clusters or NPs are constrained by the host molecules in this macrocyclic template-directed strategy. In the past few decades, the anion-template strategy has been explored and applied to synthesize high-nuclearity silver clusters because the Ag­(I) ions exhibit a soft acceptor characteristic and flexible coordination to display structural diversity, arousing the interest of synthetic scientists. − The rationale for this strategy is to use the anion as the central template core leading to the aggregation of Ag­(I) ions, which are further stabilized by the ligands such as monothiolate, ,,,,− ,− dithiolate, ,,, diphosphine, , phosphonate, carboxylate, ,,,,,,,, alkynyl ligands, ,,,,,,− metalloligand, , and their combinations. Since there are no external constraints, the cluster nuclearity can be greatly increased.…”

“…Since there are no external constraints, the cluster nuclearity can be greatly increased. The most common templates of choices are inorganic oxyanions such as NO 3 – in trigonal planar geometry, XO 4 2– (X = S, Se, Cr, Mo), − monovalent ClO 4 – , trivalent VO 4 3– , and ZO 4 3– (Z = P, As) in tetrahedral geometry, − and YO 3 2– (E = S, Se, Te) in pyramidal geometry . The volumes of the abovementioned anions are all quite close.…”

“…The carbon dioxide fixation in silver clusters sheds some light on greenhouse gas reduction. Examples of silver clusters encapsulating different shapes and sizes of such organic anion templates are rarely reported. , Only two structurally characterized Ag 18 and Ag 24 clusters encapsulating oxalate (C 2 O 4 2– ) and squarate (C 4 O 4 2– ), respectively, have been observed to date. In contrast, croconate (C 5 O 5 2– ) has never been found in the center of silver clusters, not even encapsulated in any metal clusters.…”

“…Examples of silver clusters encapsulating different shapes and sizes of such organic anion templates are rarely reported. 16,28 ) 16 and squarate (C 4 O 4 2− ), 28…”